I buy games casually.
If you're like me, you tend not to grab each new game that comes out; you prefer waiting until it seems like a good choice. Sure, the previews and exclusive reviews hype it up as the next big game, and it sure would be great to know the game before everybody else in your circle. And if it does turn out to be huge, it would be a feather in your cap to say "I had that game on day 1--I knew it was gonna be this popular." Hell, you might even get to make the first YouTube tutorial for it!
But that all comes at a cost.
If you rush out to buy each hyped game you see (OK, nobody goes out to buy PC games, but you know what I mean), you're gonna be short on money and time to play them. Even just selecting the games of particular interest to you could quickly fill your library with games that you'll only play once or twice. Games flop. We've seen 1,000 games touted as the next Half-Life, the next Civ, the next freaking Tetris--then we buy them, and they're crap. Dang, tricked again.
And sure, over time you can develop a taste for who releases great games and who doesn't, what metrics to study to see whether the new game will live up to its potential, maybe even look into the designers and search for names of specific employees on a project before making your pre-order. But that's a lot of effort for video gaming.
Personally, I go with the ultimate test: time.
Let someone else, hundreds or thousands of different people, take the bridge first while I sit back and see which bridges crumble into obscurity. Everybody who games have heard people say "oh man, you've gotta get this game--you'll love it!" when they really mean "I love this game and assume everybody else must too." Pick your reviews, learn who knows a good game when they play it, and watch which games get those reviews consistently. Sure, I'm not on the ground floor and sometimes I do miss out on the early days of games that turn out to be phenomenal. But who cares? If someone told you they bought one of the first 100 copies of TF2, would you think they had a better time than you? Meh.
Hang back, play the games you have, wait for people to push a new game to its limits and the publisher to issue patches. Wait until a few trusted friends are insisting that you personally need this game. Put it on your Wishlist, wait for Steam to have a sale, then buy it. There's nothing like making a purchase that you know will be good--it's like having a seat all warmed up for you. Comfy.